1. Technical Field
The present invention relates especially to a blower suitable in the application for cooling the so-called office automation equipments.
2. Description of the Prior Art
In the case of the prior art, the double row bearing apparatus employed in the blower for cooling the office automation equipments includes a pair of ball bearings 102 and 103 fit on the shaft 101 of the motor as shown in FIG. 8.
The inner races of the ball bearings 102, 103 are loose fit onto the shaft 101, and outer races 102b, 103b are also loose fit within the sleeve or bearing housing 104, since it is necessary to pre-load each ball bearing through an suitable means such as pre-loading spring.
It is necessary to pre-load both ball bearings 102, 103. The requirement of pre-loading the left ball bearing 102 disposed on the one side of the yoke 105 can be satisfied by applying the pre-loading force thereto through interposing a compression coil spring between the outer end face 102a of the left ball bearing 102 and the front face plate 105a of the yoke integrally connected with the front face plate 108a of the impeller 108. As for the stop ring 107 secured to left end portion of the shaft 101 is required to hold the ball bearing 103.
In the case of the pre-loading means as shown in FIG. 9, it is difficult to apply an appropriate pre-loading force to the bearing. This is because the space defined between the yoke 105 and the ball bearing 102 is too small to accommodate the compression coil spring 106 of the sufficient size to pre-load the bearing properly.
Further, the clearances present between the bearing and the sleeve and/or the shaft will cause upon rotation of the impeller a rotational run out in both radial and thrust directions. This rotational run out will cause noises, affect the blowing characteristics, and reduce the lifetime of the bearing.
The assembling operation of the compression coil spring 106 can not be effected easily since the compression coil spring should be inserted into a limited space against the repulsion of the spring.
The sleeve has at both ends thereof larger inner diameter portions 104a, 104b for accommodating the outer races of the ball bearings. Each of the larger inner diameter portions includes a shoulder respectively to which the outer race of the ball bearing will be abutted. When the larger inner diameter portions 104a, 104b are more or less eccentrically formed with respect to the sleeve, the rotational movement of the shaft is also effected eccentrically, and generate vibrations or noises. In this connection, a precise machining on the larger inner diameter portions is required strictly.
As can be seen from the above, the blower employing the double row bearing apparatus of the prior art requires a pair of ball bearings including an inner and outer races, a stop ring, and a pre-loading spring. Of course, the assembling operations for these components are also necessary. This involves a high cost for manufacturing the bearing apparatus.
The more the diameter of the shaft of the motor, the more the rigidity of the shaft, and thus the rotational run out is reduced, and the motor of quiet and high durability can be obtained. However, the diameter of the shaft of the bearing apparatus of the prior art is smaller than that of the sleeve by twice the sum of the thicknesses of inner and outer races of the ball bearings fit around the shaft. In this connection, it is difficult to provide the shaft of good durability, reduced in rotational run out, and reduced in the generation of the vibration or noises.
Accordingly the object of the present invention is to provide a blower comprising a bearing structure wherein the number of components are reduced, the cost for manufacturing can be reduced, and the diameter of the shaft can be increased. The bearing structure in the present invention is good at its durability, eliminate or reduce the rotational run out, and provides outstanding quietness.
These and other objects are achieved by a blower in accordance with claim 1 having an impeller adapted to be rotated upon energizing the blower comprising;
a bearing apparatus for supporting a rotational center portion of the impeller, the bearing apparatus including;
a sleeve,
a stepped shaft including a larger diameter portion and a reduced diameter portion provided at one end thereof,
the first rolling contact groove formed at an appropriate position around the outer peripheral surface of the larger diameter portion,
the second rolling contact groove formed on an inner peripheral surface of the sleeve so as to correspond with the first rolling contact groove,
balls of the first row interposed between the first and second grooves,
an inner race fit over the reduced diameter portion and secured thereto with an appropriate pre-loading force,
the third rolling contact groove formed around an outer peripheral surface of the inner race,
the fourth rolling contact groove formed on the inner peripheral surface of the sleeve so as to correspond with the third rolling contact groove, and
balls of the second row interposed between the third and fourth grooves.
The blower in accordance with claim 2 comprising;
a frame including a base connected through stays to the frame so as to be positioned at the central portion of the frame,
a cylindrical bearing member formed integrally with the base to extend therefrom fowardly,
a stator including an iron core and a coil and mounted on the exterior of the cylindrical bearing member,
an impeller including a front face plate, a flange formed over the outer periphery of the front face plate, and suitable numbers of blades provided on the outer periphery of the flange,
a yoke including a front face plate to which the front face plate of the impeller is secured, a flange formed over the outer periphery of the front face plate, magnet or magnets mounted on the flange, and
a bearing apparatus for supporting the central portion of the yoke through a shaft of the bearing apparatus to which the central portion of the yoke is fit and secured thereto, the bearing apparatus including;
a sleeve,
a stepped shaft including a larger diameter portion and a reduced diameter portion provided at one end thereof,
the first rolling contact groove formed at an appropriate position around the outer peripheral surface of the larger diameter portion,
the second rolling contact groove formed on an inner peripheral surface of the sleeve so -as to correspond with the first rolling contact groove,
balls of the first row interposed between the first and second grooves,
an inner race fit over the reduced diameter portion and secured thereto with an appropriate pre-loading force,
the third rolling contact groove formed around an outer peripheral surface of the inner race,
the fourth rolling contact groove formed on the inner peripheral surface of the sleeve so as to correspond with the third rolling contact groove, and
balls of the second row interposed between the third and fourth grooves.
The blower in accordance with claim 3 comprising;
a frame including a base connected through stays to the frame so as to be positioned at the central portion of the frame,
a cylindrical bearing member formed integrally with the base to extend therefrom fowardly,
a stator including an iron core and a coil and mounted on the exterior of the cylindrical bearing member,
an impeller including a front face plate, a flange formed over the outer periphery of the front face plate, and suitable numbers of blades provided on the outer periphery of the flange,
a yoke including a front face plate to which the front face plate of the impeller is secured, a flange formed over the outer periphery of the front face plate, magnet or magnets mounted on the flange, and
a bearing apparatus for supporting the central portion of the yoke through a sleeve of the bearing apparatus to which the central portion of the yoke is fit and secured thereto, the bearing apparatus including;
a sleeve,
a stepped shaft including a larger diameter portion and a reduced diameter portion provided at one end thereof,
the first rolling contact groove formed at an appropriate position around the outer peripheral surface of the larger diameter portion,
the second rolling contact groove formed on an inner peripheral surface of the sleeve so as to correspond with the first rolling contact groove,
balls of the first row interposed between the first and second grooves,
an inner race fit over the reduced diameter portion and secured thereto with an appropriate pre-loading force,
the third rolling contact groove formed around an outer peripheral surface of the inner race,
the fourth rolling contact groove formed on the inner peripheral surface of the sleeve so as to correspond with the third rolling contact groove, and
balls of the second row interposed between the third and fourth grooves.
The blower in accordance with claim 4 comprising;
a frame including a base connected through stays to the frame so as to be positioned at the central portion of the frame,
a cylindrical bearing member formed integrally with the base to extend therefrom fowardly,
a stator including an iron core and a coil and mounted on the exterior of the cylindrical bearing member,
an impeller including a front face plate, a flange formed over the outer periphery of the front face plate, and suitable numbers of blades provided on the outer periphery of the flange,
a yoke including a front face plate to which the front face plate of the impeller is secured, a flange formed over the outer periphery of the front face plate, magnet or magnets mounted on the flange, and
a bearing apparatus for supporting the central portion of the yoke through a sleeve thereof to which the central portion of the yoke is fit and secured thereto, the bearing apparatus including;
a sleeve,
a stepped shaft including a larger diameter portion and a reduced diameter portion provided at one end thereof,
the first rolling contact groove formed at an appropriate position around the outer peripheral surface of the larger diameter portion,
the second rolling contact groove formed on an inner peripheral surface of the sleeve so as to correspond with the first rolling contact groove,
balls of the first row interposed between the first and second grooves,
an inner race fit over the reduced diameter portion and secured thereto with an appropriate pre-loading force,
the third rolling contact groove formed around an outer peripheral surface of the inner race,
the fourth rolling contact groove formed on the inner peripheral surface of the sleeve so as to correspond with the third rolling contact groove, and
balls of the second row interposed between the third and fourth grooves, wherein
the bearing apparatus is provided within the cylindrical bearing member so that the sleeve can be rotated around the axis of the bearing apparatus, and the end of the shaft is secured to the base.
The blower in accordance with claim 5 comprising;
a frame including a base connected through stays to the frame so as to be positioned at the central portion of the frame,
a stator including an iron core and a coil and mounted on the inner peripheral surface of a flange extending fowardly from an outer periphery of the base,
an impeller including a front face plate, a flange formed over the outer periphery of the front face plate, and suitable numbers of blades provided on the outer periphery of the flange,
a bearing apparatus for supporting the central portion of a supporting plate mounted on the rear surface of the front face plate, the bearing apparatus including;
a sleeve to which the central portion of the supporting plate is fit and secured,
a stepped shaft including a larger diameter portion and a reduced diameter portion provided at one end thereof,
the first rolling contact groove formed at an appropriate position around the outer peripheral surface of the larger diameter portion,
the second rolling contact groove formed on an inner peripheral surface of the sleeve so as to correspond with the first rolling contact groove,
balls of the first row interposed between the first and second grooves,
an inner race fit over the reduced diameter portion and secured thereto with an appropriate pre-loading force,
the third rolling contact groove formed around an outer peripheral surface of the inner race,
the fourth rolling contact groove formed on the inner peripheral surface of the sleeve so as to correspond with the third rolling contact groove, and
balls of the second row interposed between the third and fourth grooves, wherein
the exterior of the sleeve of the bearing apparatus is provided with a cylindrical yoke on which a magnet or magnets corresponding to the coil of the stator is provided, and the end of the shaft is secured to the base.
In the blower in accordance with claim 6, the balls for the first and second rows of any of claims 1 to 5, are made of ceramic material.
In the blower in accordance with claim 7, the outer diameter of the inner race of any of claims 1 to 5 are the same as that of the larger diameter portion of the shaft, and the diameter of the balls for the first row is the same as that of the balls for the second row.